Typically, a grinder tool is used to grind and polish slabs a stone, such as marble and granite, through a rotatable grinding wheel that is covered by a polishing pad. The pad typically has a specific grit for the type of stone being worked on and the desired appearance for the stone. The wheel passes along the surface of the stone to create the desired grinding and/or polishing effect. Ideally, the grinder tool has to be used in the most uniform possible manner for the best polishing and for the longest life of the tool itself. This uniformity required many passes over the same surface area of the stone slab to achieve the desired appearance for the slab.
The inventor knew that grinder machines for polishing marble were available with a single grinder head having a radial grinder wheel and an attached pad. Typically, the grinder wheel rotates about a vertical axis while the grinder tools oscillates about its horizontal axis. The grinder tool generally has a curved working surface and therefore the tool working surface is substantially reduced to a constantly changing line.
The inventor was also aware that it was often necessary to grind the edges of a slab of stone. The edges were grinded to chamfer soft edges, create decorative bevels, or form a mating surface for two or more slabs. Through years of experience, the inventor recognized that there were several different kinds and sizes of stone edger tools that were used in the field. One such edger was used for shaping the edge of a stone countertop. This edger had a housing with an internal electric motor and a bit extending below the surface of the housing. In use, the housing rested on the level counter surface while the motor spins the bit and the user guides the bit along the edge of the counter surface smoothing and shaping the edge of the stone counter.
However, the inventor quickly recognized that the problem with this type of edger is that the internal motor makes it heavy and difficult to transport and maneuver over the counter surface. Further, the weight of the motor of the edger causes friction between the lower surface of the housing and the stone countertop as the device moves across the countertop. The friction can cause scratches in the stone's surface. Another problem with this type of edger is that it is relatively expensive to purchase and maintain because of the many moving parts that comprise the gears and internal motor.
The inventor was also familiar with another edger, often referred to as a stone polisher. The inventor had used a stone polisher before, and knew that stone polishers were essential tool for stone workmen. The inventor had often used a stone polisher in the past. The stone polisher is a small hand tool comprising a rotating shaft and wheel able to combine with various bits for etching, polishing, and cutting slab materials such as stone. Stone polishers were generally powered pneumatically or electrically.
The inventor, though, recognized that the problem with using a stone polisher as an edger is that stone polishers do not have housings or other guides for aligning and squaring them with the stone. This makes it difficult to form consistent cuts and profiles in stone edges because the angle of the stone polisher relative to the stone's edge is hard to keep consistent. This can lead to more time spent by the stone workman, which means more expense to finish the stone product.
The inventor decide to fabricate a grinder tool that was lightweight and had a small motor, so that the tool could be carried to the stone slab, rather than the slab having to be moved. The inventor realized that a smaller grinder tool could be effective in making smaller cuts and profiles, especially on the edge of the slab. However, the tool was still too slow and required multiple passes along the edge of the stone slab.
Through trial and error, the inventor realized that the efficiency and effectiveness of polishing stones depended on the number of the wheels and pads that could be carried by the tool. By adding multiple wheels along the tool, the grinding surface area along the longitudinal axis of the edge of the slab was expanded. The inventor also recognized that powering a single central wheel saved energy.
After further trial and error, the inventor added different pads on each wheel. The inventor knew that the grit on each pad affected the speed of the grinding process. The inventor recognized that diamond grinding cup wheels are used in different-roughness grindings. For coarse grinding, the bond may be softer and the diamonds' quality higher, because in this case the diamonds are more easily to become blunt.
The inventor knew that in this case, the diamond grit should be bigger, normally from 35 grit to 50 grit. For this is coarse grinding and big grit can improve the working efficiency of the tool. However, for fine grinding, i.e., polishing, the bond may be harder and the diamonds' quality lower. The inventor knew that this was because the diamonds can last longer and hard bond can also help the precision of the processing. For polishing, the diamond grit is normally between 80 grit to 120 grit, depending on the grinding requirements.
However, the inventor saw that the pads were overheating. The inventor knew that a coolant, such as water was often used while grinding stone slabs. The inventor decided to add a fluid inlet that carried water from an outside water source to the tool. The fluid inlet included tubing that directed water onto the pads during their rotation. The water prevented overheating of the pads and helped maintain the grinder tool at optimal efficiency during operation.
Stone grinder tools have been used for economically and efficiently polishing marble and granite in the past, yet none with the present characteristics of the present invention. See U.S. Pat. No. 601,668; U.S. Pat. No. 5,454,751; and U.S. Pat. No. 8,436,624.
For the foregoing reasons, there is a need for a system and method for grinding the edges of stone slabs with a multi-wheel grinder tool that is lightweight and maneuverable.